John Maynard Smith and Eors Szathmary boldly expanded the symbiotic cell theory of Lynn Margulis to include other major transitions. They were a bit timid in their discussion of human evolution, however, restricting themselves to the genetic basis of language. Now it appears likely that human evolution was a full-fledged major transition. The reason that we are so unique among primates is because our ancestors became the primate equivalent of a single organism or a social insect colony.
Recall that the key ingredient of a major transition is the suppression of fitness differences within groups, causing between-group selection to become the primary evolutionary force. In most primate species, including our closest ancestors, intense within-group competition limits the opportunities for cooperation among members of the group. This is in contrast to extant human hunter-gatherer societies, which are fiercely egalitarian. What accounts for this shift and when did it occur in human evolution?

Humans are incomparably better at throwing projectiles than other primates, an ability that required whole-body anatomical changes and evolved early in the hominid lineage. Although the original purpose of throwing was presumably to deter predators and competing scavengers, it could also be used to suppress bullying and other domineering behaviors within-groups. This hypothesis, developed by Paul Bingham, is a specific version of a more general hypothesis of guarded egalitarianism, originally advanced by Christopher Boehm on the basis of the egalitarian nature of most extant hunter-gatherer societies. However it was accomplished, guarded egalitarianism provides the key ingredient of an evolutionary transition.

It has been common in the past to regard advanced human cognitive abilities, such as a theory of mind, as the first step of human evolution that made widespread cooperation possible. Now it appears that the sequence needs to be reversed. The first event was the suppression of fitness differences within groups, which did not require a change in cognitive ability. Then, between-group selection favored forms of mental cooperation in addition to physical cooperation. After all, symbolic thought and the social transmission of behaviors are fundamentally cooperative activities that are unlikely to take place among uncooperative individuals. Even human capacities that we take for granted, such as the communicative nature of our eyes, our ability to point, and awareness of others that emerges early in infancy, are forms of cooperation that appear to be uniquely human. Michael Tomasello and Jonathan Haidt are two prominent researchers developing this thesis.

In retrospect, human evolution has all the hallmarks of a major transition. It was a rare event, occurring only once among primates. It had momentous consequences; cooperation enabled our ancestors to spread over planet, eliminating other hominids and many other species along the way. We also diversified to occupy all climatic zones and hundreds of ecological niches, although by cultural evolution rather than genetic evolution. The advent of agriculture enabled us to increase the scale of society by many orders of magnitude by a process of cultural multilevel selection. Finally, the transition was not complete. Within-group selection still takes place and is merely suppressed compared to between-group selection.

Peter Richerson, who pioneered the modern study of cultural evolution with Robert Boyd, likes to call human groups crude superorganisms, cooperative units to be sure, but not in the same league as bodies or beehives. I’m happy with this qualifier, but even thinking of human groups as crude superorganisms has vast implications, especially against the background of individualism that has dominated the intellectual landscape for the last half century. The corpus of Pete and Rob’s work leaves little doubt that cultural change is both an evolutionary process and a multilevel evolutionary process in which group selection can seldom be ignored. No wonder our students think so naturally in terms of “for the good of the group”. We are a highly group-selected species.

Comments

One thing I’ve noticed about superorganisms is how simple the individual members are. Even mole rats are simple creatures. My point is, when you get to something as complex as a human being, you have a species that makes up something more than a superorganism. Think of it rather as a meta-organism, where the members are capable of complex behaviors themselves, and producing complex group behaviors in concert with other members of their group.

In such a situation it is not a case of group selection vs. individual, but in how group selection impacts individual selection and individual selection impacts group. Among humans it becomes a matter of how the group affects individual fitness, and how fitness within the group affects environmental fitness. So that dark skin color among Australian Aborigines remains desirable because even southern most Tasmania really isn’t all that close to the Antarctic Circle. Certainly not intruding into the Antarctic the way North America and Northern Eurasia do.

In short, it’s not as simple as individual or group selection where humans are concerned. Both play a role, and fitness within a group affects and shapes group fitness as a whole.

I find group selection an attractive idea, but it’s easy to be a killjoy and say:

Even when altruism is selected-for in cases where members can walk away, altruism is still an individual’s strategy for succeeding in a walk-away environment. And they are succeeding individually or else their genes would disappear.

But there is an even more troublesome argument…

I can look at a single cell chugging along with all of its biological processes, and say:
Everything in this view is explainable by physics; everything is explainable by the interaction of particles and fields. Therefore ‘biology’ is an unnecessary explanation for anything.

I’m not sure how we argue our way out of this box. We like to say that higher-level abstractions exist, but they really don’t, they are just ideas. Nature runs at the machine-code level in all cases.

“Nature runs at the machine-code level in all cases.” Perhaps. Perhaps not.

Biology is concerned with the strategies of life forms. Which in turn depend on the strategic nature of life’s physical properties and their interaction. The difference seems to be that life forms its own strategies, and/or accelerates the formation of nature’s physical strategies, which we can try to observe in real time. We know a lot less about the formation of physical strategies that have been so consistently effective over the eons on a universal scale.
Was there an event in the distant past that made strategic choices such as life does today and that helped in the selection of what we regard as the laws of physics? Or has there been a continual presence of such strategic operations in the cosmos forever? We can only make some educationed speculation to get closer to an answer. Biology represents our attempts to do so. Perhaps we should see or recognize biology as a form or aspect of philosophy in that respect. And physics as another. And in fact we already have:

I hope the continuation will include some evidence for the claims made here. For example, that extant human hunter-gatherer societies really are more integrated than other primate groups. And then that this has lead to suppression of within-group fitness differences. Otherwise we’re back with speculation.

I’m actually doing research in philosophy of science (biology and cognitive neuroscience mostly, but reductionism is an all time fav) – and I think it’s pretty straightforwardly true that all causal interactions come down to the lowest physical level – and since everything is made up out of the basic physical entities, it would take some magic additional causal forces with no physical basis in order for higher levels to describe independent things.
BUT – basic physical entities realize various types of entities we pick out at higher levels. And this means that there are regularities for specific types of physically realized entities for which it makes no sense to describe them at the physical level, because a myriad of different specific configurations can realize the same type, which is defined functionally. So, while ontologically, everything reduces to the physical, there are functional regularities at higher levels, which is why there is – descriptive/explanatory autonomy of the higher level sciences.

Btw, wikipedia isn’t that good a resource when it comes to this. The best resource I know is the Stanford encyclopedia of philosophy. Here are two relevant links:

The view MikeB describes is sometimes referred to as the “multiple realizability” thesis. In addition to being influential in philosophy of biology, it also is crucial for functionalist approaches in philosophy of mind. Jerry Fodor has been mining these hills for about 40 years.

thanks for providing the additional info – but while multiple realizability is usually taken as an argument against reductionism, especially in philosophy of mind, I didn’t mean to offer it as such. In fact, I think it is perfectly compatible with reductionism properly understood, namely in form of realization physicalism (see the book Andrew Melnyk).
Physical entities and processes therein can be completely reducible without that meaning that a functional type cannot be realized by multiple physical tokens. For real-world systems, it is usually the spatial organization and interaction of the physical parts that make something a token of a specific type. All entities in the world are still physical and they fulfill their functional roles in virtue of their physical organization and its relation to other such entities and processes.

All I’m saying is that we can acknowledge multiple realizability without having to give up reductionism/physicalism.

P.S.: The Stanford Encyclopedia also has brilliant arguments on reductionism and physicalism in philosophy of mind and a lot of other topics (like “animal cognition”). Most valuable resource I’ve ever had.

As to which has the better summation concerning Philosophy of Biology and the directions it has taken, it’s hard to say because neither seems to go far enough. Wikipedia mentions “What is Life?” as a topic under discussion but that’s the end of it. In the Stanford Version, that’s not even a related entry.

It is my understanding that human females are pretty unique among animals in being willing to care for and foster infants they are not related to. I did a little looking on PubMed and didn’t find very much on non-human fostering.

On thinking a little more, ants and bees do that too, so much so that non-ants and bees can parasitize them by mimicking the signals.

Reductionism is really just a philosophical issue: Physical laws and particle behavior are not going to tell us anything about group selection vs. individual selection. Physicists can’t even reliably predict the the behavior of elements from basic principles, let alone cells and organisms. So biology is obviously necessary from a practical perspective. Or do you want your physician to be a physicist?
Also, saying individuals that benefit from group selection are by definition more fit as individuals, does not disprove group selection. That is, if those individuals that benefit are more fit only because of group selection, then we should recognize that higher level selection is occurring.

I agree with noel that we shouldn’t get too worked up about things like reductionism, especially without specifying precisely what we mean by the term. And to pursue the computer analogy… of course(!) real world computations can always be described at the “machine code level”. Nobody has suggested otherwise. But only people who have never done any programming would think that that makes “higher level” languages irrelevant to understanding computation.

It is my understanding that human females are pretty unique among animals in being willing to care for and foster infants they are not related to.

There are cooperatively breeding birds in Australia that do it too (sorry, can’t remember the species: heard about it a long time ago). Plus, eider will look after unrelated young in their creches. Actually, this is selfishness: the unrelated young are kept to the outside of the creche, where they are more likely to be predated upon. I’m sure there are more examples too.

“There are cooperatively breeding birds in Australia that do it too (sorry, can’t remember the species: heard about it a long time ago). Plus, eider will look after unrelated young in their creches. Actually, this is selfishness: the unrelated young are kept to the outside of the creche, where they are more likely to be predated upon. I’m sure there are more examples too.”

There are indeed other examples. Ostriches are the classic example, but it also occurs in old world primates from macaques through the great apes.

John Atkeson wrote: “We like to say that higher-level abstractions exist, but they really don’t, they are just ideas. Nature runs at the machine-code level in all cases.”

I disagree with the first sentence here, but not the second. I think higher order phenomena appearing as abstractions from below can manifest and exist at higher levels of organization. I would argue that organisms are an example. In fact, I would argue that everything other than perhaps quarks fit this description. This presents a fundamental problem for the issue of group selection, because we look up at this level from below. That makes it look like an abstraction to us even when the groups have manifested as real agents of interaction.

Emergence of higher order entities is always build on the “machine code” at the bottom, even though the phenomenology of higher order existence can exhibit qualities that are consistent with, but not easily attributable to, the “machine code”.